Shanklin made his Wales debut against Japan in 2001, while playing his club rugby with Saracens. He became a dependable presence in the Wales midfield, with an excellent scoring record at both international and domestic level.

He held dual residency with both Wales and England, having been born in Harrow, but chose to follow his father, Jim, into a Wales shirt. He played his first top level rugby for London Welsh before joining Saracens in 1999. Shanklin played for the London side for four seasons before becoming one of Cardiff Blues' first signings in 2003.

He was by this point an established international, having made his Six Nations debut against France in 2002. He was selected by Steve Hansen for the 2003 Rugby World Cup in Australia, playing in Pool games against Tonga and New Zealand, notching a try in the latter.

His first taste of genuine success at international level came in the 2005 Six Nations when, in tandem with Gavin Henson, he formed arguably the best centre partnership in Europe as Wales won their first Grand Slam in nearly 30 years.

Shanklin's excellent form during the tournament led to his selection for the 2005 British & Irish Lions tour to New Zealand, although a career threatening knee injury would end his tour before the Test matches. The injury would wipe out his 2005-06 season, with question marks remaining over whether a return to playing would be possible.

His eventual return came at the start of the 2006-07 season with the Blues, and then for Wales in the autumn international against Australia at the Millennium Stadium. Shanklin soon returned to form approaching his best, and was again a regular in the Welsh setup. His first Six Nations back from injury in 2007 was a disappointing one, as Wales could only register a single win against England.

Selection for the Rugby World Cup squad was assured with some fine end-of-season displays for the Blues, but poor Welsh performances at the finals saw Shanklin again exiting a World Cup early.

Under new Wales coach Warren Gatland, Shanklin was at first left on the bench for the Six Nations opener against England. After replacing Sonny Parker his influence was immediately apparent as Wales stormed back into the match, and he started the remaining games as he claimed his second Grand Slam in four seasons.

He was also a key member of Wales squad that went close to securing back-to-back Championships the following year - only to be pipped by Ireland. His form was rewarded with a place in the British & Irish Lions squad for that year's tour to South Africa but a shoulder injury suffered on Magners League duty with the Blues ended his tour before it had begun.

Again he fought back and enjoyed two further seasons with the Blues, and further honours with Wales, but he was forced to announce his retirement from the game in April 2011, having finally succumbed to his troublesome knee.